David danielsson



DVDANIELSSON.

THERMIC TIMING ELEMENT. APPLICATION FILED APR.I0.1918.

WTNESSES:

ATTORNEY Patented Sept. 16, M19.

DAVID DANinLssoN, or vlismnns, SWEDEN.

THERMIC TIMING ELEMENT.

Specification of Letters atent. Patented Sept. 16), 1919.

Application filed April 10, 1918. Serial No. 227,657.

lays, which means that the time necessary' for the releasing action varies inversely as the current. Among other principles,- it has been proposedto utilize the thermic effect of the current for this purpose, whereby, as is well understood, the same effect can be o'btained by a large current in a short time` as. by a small current in a longtime. The diiiiculty in such constructions has however been to make' them independent of u'ctuations in the surrounding temperature so as to aict in exactly the same time whether they are placed in a machine room or the like with for instance a temperature of 100o F.

. or outdoors in a temperature considerably Ybelow zero.

For effecting such compensationfor surrounding temperature fluctuations, it has already been proposed to compose the active portion of the relay of two parallel, or nearly parallel, substantially equal metal parts, the free ends of which act upon one member in such manner, that the latter will be rotated when the expansion of the metal parts is unequal, but only slightly displaced, at equal expansion. The constructions of this kind have, however, hitherto been such that either aninferior mechanical stability or too little sensitiveness has been obtained The present invention has for its ob]ect 4to provide an improved thermic timing element of the aforesaid compensated type. The principal distinguishing feature of the said timing element is that the two active metal parts consist of band portions rulining over .a roller pivoted in Y, bearings.

Hereby the heat capacity can be kept very small and thus the sensitiveness high, as the band portions can be made rather thin. In they same time the mechanical stabi-lity will be satisfactory by reason of the positive pivoting support of the roller. The two band portions preferably may form ortions df the same band which may be laid in U- or V-sha'pe around the roller and secured thereto at one or more points.

Some forms of the invention are illustrated in the accompanying drawing. Figure 1 shows one form of a timing element in a side view. Figs. 2 and 3 show modifications of a detail of Fig. 1 in order to obtain a greater or smallersensitiveness. Fig. 4 shows another modication of the same detail in order to vary the sensitiveness. Fig. 5 shows diagrammatically a combination of two timing elements, in order to obtain Aa special differential action. Fig. 6 shows a device with one timing element acting in substantially the same manner as the two timing elements of Fig. 5;

In l, 1 is a metal band, the ends of which are secured between clamping pieces 2 1 while its middle portion partially surrounds a little roller 3 and is secured thereto by means of a clamping piece 4 and a screw 5. The roller 3 is pivotally mounted in a pair of levers 6 (only one being shown, for the sake o-f clearness), which are rotatable on a pin 7 and actuated by springs 8 in such sense as to tighten the band. The roller 3 carries a` radially projecting pin 9, and against the free end of thev latter an arm 10 rests under the action of a spring 11.

To one portion of the band 1, there is secured a heating element consisting of a re- .sistance wire 13 wound on a core y12 of mica soy a small portion of the heat is transmitted thereto. This expansion will cause a displacement of the upper end of the pin 9 (to the left hand side in Fig. 1,). As long as the current does not exceed a certain permissible value, there will be no further consequence. If, however, such` an excess takes place during a shorter or longer timedepending upon the heat capacity of the heated parts-the band will expand suiiiciently to cause a sufficient rotation of the roller 3 to release the arm 10. The latter then is swung by the action lof spring. 11 until it strikes a stop and this movement can be utilized for different purposes, for instance to release a circuit breaker. The Spring 11, in the form shown, acts in such manner on the arm 10 as to eXert normally a comparatively small turning movement. In releasing, however,

the leven arm of the spring is rapidly in-4 creased, and thus the arm 10 will be able to perform a comparatively powerful action.

"It is obvious from the description that the timing element will act in a time varying inversely as the current traversing the heating element. It is also obvious, that any fluctuation in the surrounding temperature only will cause a uniformexpansion or contracmentioned, except the arm 10 and the spring 11, is journaled on a pin 15 parallel to the roller 3, and is adjustable around said pin by means of ascrew 16. It is obvious, that such an adjustment alters the angle through Which the roller 3 must rotate before the l arm 1 0 is released, and thereby changes the /sensitiveness of the timing element.

The sensitiveness may be read by means of a pointer 17 and a scale or dial 18 which can be made to read directly in amperes or seconds. f

Fig. 2 shows another form of the heating element, the latter consisting only of a portion of the band 1, traversed by the current. By this means, the heat capacity Will be the smallest possible, and thus the sensitiveness of the timing element very large..

Fig. 3, on the contrary, shows a heating d evice with a comparatively large heat capacity and hence of little sensitiveness. This is accomplished by means of a special'metal mass 20 secured to the band 1 on the opposite side to that carrying theheating `element 13. Other details of the timing 'element except the portion of the band carrying or forming the heating element, are Supl posed to be quite the same in Figs. 2 and 3 as in Fig. 1.

4: shows a modied device for adjusting the sensitiveness of the timing element, only the details affected by said modication being shown, Adjacent to one 0f -the clamping pieces 2 for the band here is arranged a set screw 19 for tightening moreor less the corresponding` band portion. Of

course such adjusting also may be effected in the well known manner by connecting resistances in parallel with the timing element.

A timing element embodying the present invention can be employed in other combinations than as a simple overload relay, as hitherto described. For instance, it may be arranged according to Figs. 5 or 6 to protect a three phase system against a certain a certain degree of unbalancing. I n Fig. 5, two bands 1 arranged in mechanical respect as in anyone of Figs. 1A and only dia- 'gramniatically shown, are combined and so arranged, that two of the phase wires of Va three phase system act upon each of two band portions while the third phase wire acts upon the two remaining portions. It is easily seen, that any dissymmetry of the currents exceeding a certain valuedepending for instance on an interruption or the grounding of a phase wire-fwill cause a rotation of one of the rollers 3 which motion may be utilized for. actuating a circuit breaker. The same action can be obtained by an arrangement according to Fig. 6, where two phase wires act upon one band portion, each by its heating element, and the third phase wire upon the remaining portion. Having now particularly described an ascertained my invention and the manner of its operation, I declare that what I claim is: l

1. A thermic inverse time limit element comprising a roller pivoted in bearings, band portions connecting said roller to a frame, means for tightening said -band portions, `a current traversed heating element acting on said band, a radially -projecting pin carried by said roller, an arm normallyl resting against said pin, and means for keeping said arm against said pin.

2. A thermic inverse time Ilimit element comprising a roller pivoted in bearings, band portions connecting said roller to al frame, means for tightening said band portions.l a current traversed heating element acting on saidv band, a radially projecting pin carried by said roller, an arm normally resting against said pin, and resilient means for ykeeping said arm against said pin.

3. A thermic inverse 4time limit element comprising a roller pivoted in bearings, band portions connecting said roller to a frame, means for tighteningsaid band portions, a current traversed heating element acting on said band, a radially projecting pin carried by said roller, an arm normally resting against said pin, means for keeping said arm against said pin, and resilient means arranged to normally exert a comparatively small turning moment to said arm and operable, when the arm is released, to give the latter a comparatively powerful action.

v4. A thermic inverse time limit element, comprising in combination, a` roller pivoted in bearings, two substantially parallel band portions connecting said roller to a frame, a stretching device acting on said roller to tighten the band portions, a current tra-y versed heating element acting on said band, an operating pin projecting from said roller so as to be rotated therewith,4 an arm normally resting against the end of said pin, and a spring actlng upon said arm, normally under a small angle, to keep it against said 1n. p 5. A thermic inverse time limit element comprising a roller pivoted in bearings, band portions connecting said roller to a frame, means for tightenin said band por tions, a current traversed eating element acting on said band, a radially projecting pin carried by said roller, an arm normally resting against said pin, means for keeping H said arm against said pin, and means for changing the sensitiveness of said element.`

6; A thermic inverse timelimit element comprisingl a. rollerpivoted 1n bearings, a

band portion connecting said roller to a frame, means for tightening said band p0r- 't1on, a current traversed heating element acting on said band, a radially projecting pin carried by said roller, an arm normally resting againstl said pin, means for keeping said arm against said pin, and a pivoted frame supporting said. members, except the varm and having means for adjusting its pivot.

In testimony whereof I have affixed my signature hereunto in the presence of two subscribing Witnesses.

- DAVID DANIELSSON.

Witnesses: 4

BIRGER NORDFELDT, R. LEVENIUS. 

